Power of the Sun
One thing that I did not evaluate on this project was the "heat effect".
Not the heat coming from the RPi board. Yes the two heatsinks get a little warm when cpu is running full speed, but this is a very low computational prj, and so that was not my problem.
Today was the very first bright and sunny day since I started this monitoring. So Ieft my prototype on my window for few hours and after a couple of hours I noticed there were no more data update on this website.... mmm.... mumble.
I did an ssh on the RPi board and it was still alive, but I started to see weird errors about binary not being executed and filesystem being corrupted. So I went to check the board ad it was HOT, really hot. Heatsinks were untouchable and the sdcard was super warm.
So what happened? the enclosure is the issue.
I was using a clear enclosure like the one in the picture. I got it toghetert with the board from element14/farnell.com.
The enclosure has no ventilation, it;s all closed. The sun was not even comparable to the level of radiation I will find in a summer afternoon, but it was strong enough to kill my board in 2h.
The sdcard was completely corrupted, and the whole board was very warm.
It seems that RPi is not yet ready for "tropicalization" and won't last long time if you leave it under the direct sun without protection and ventilation.
I had to format my sdcard, let the board cool off whyle I was preparing the system again ... Oh well ... now I know.
So the conclusion is that I won't use this kind of plastic boxes at all.
I will have plan for an enclosure that does contain all the parts, protect from rain, but also does allow some ventilation to keep the insde on the cool side.
I've found this really awesome aluminum case (specific for RPi board) that would have been the safest enclosure, since it is a perfect protection and also allow for heat dissipation. Most important it would not let the sun heting the inside part of the box. But it is way too expensive (70$) http://www.raspberry-pi-case.com/
I think I will use those solar-powered fans to automatically have some "forced" ventilation during the sunny days.